Validation of gamma scanning method for optimizing NaI(Tl) detector model in Monte Carlo simulation

• Published in: Applied radiation and isotopes 2019-07, Vol.149, p.1-8
• Main Authors: Chuong, Huynh Dinh, Hung, Nguyen Quoc, My Le, Nguyen Thi, Nguyen, Vo Hoang, Thanh, Tran Thien
• Format: Article
• Language: English
• Subjects: Efficiency calibration; Gamma scanning; MCNP6 code; Monte Carlo simulation; NaI(Tl) detector
• ISSN: 0969-8043; 1872-9800
• DOI: 10.1016/j.apradiso.2019.04.009

The aim of this study is the validation of gamma scanning method for optimizing NaI(Tl) detector model in Monte Carlo simulation. The experimental procedure involved: scanning on front and lateral surfaces of the detector with collimated low-energy photon beam; calibrating the efficiency with energies between 31-1408 keV for point sources at distances of 0 cm and 30 cm from source to the detector. The Monte Carlo code used for the simulations was MCNP6. The diameter and the length of crystal were determined according to the measured results of gamma scanning with a collimated 241Am radioactive source. The distance from window to crystal was estimated using transmission measurement recorded on a second detector. The density of reflector was adjusted to obtain the match between measured and simulated values of efficiency ratio of 81 and 31 keV from a 133Ba radioactive source. The optimized model was applied in Monte Carlo simulations to determine the efficiency and energy spectrum response function of NaI(Tl) detector for point source measurements in two configurations. Good agreement was obtained between measured and simulated results. •A model for NaI(Tl) detector was optimized according to the experimental results of the scanning on front and lateral surfaces of the detector with a collimated low-energy photon beams.•The measured efficiencies with energies between 30 and 1408 keV for point sources at distances of 0 cm and 30 cm from source to detector were determined.•The simulated efficiencies were calculated using MCNP6 code.•Good agreement was obtained between measured and simulated efficiencies for the optimized model.